Integrated circuits of today typically include numerous devices (e.g., millions or even billions of devices) in order to perform their intended operations. One of the most common devices used in integrated circuits is the complementary metal oxide semiconductor field effect transistor (CMOSFET or CMOS, for short). Some CMOS devices are employed to process signals residing internally within integrated circuits. Other CMOS devices are implemented at the periphery of integrated circuits, such as in input/output (I/O) circuits, to receive input data or signaling for the integrated circuits or produce output data or signaling for devices external to the integrated circuits.
Often, I/O drivers are configured to receive or output data or signaling with defined voltage levels. For example, some I/O drivers are required to generate digital data or signaling with defined voltage levels of zero (0) and +3.6V. However, the non-I/O driver devices internal to integrated circuits may not have such voltage level requirements. In many cases, it is desirable to operate the non-I/O driver devices at much lower voltages in order to process the data or signaling at a much faster rate. For example, it may be desirable to operate CMOS devices at defined voltage levels of zero (0) and +1.8V.
However, employing two or more different types of CMOS, such as lower voltage CMOS devices for non-I/O applications and higher voltage CMOS devices for I/O applications, is not generally desirable since it requires more masks and more processing steps to manufacture the integrated circuits. Generally, the higher number of masks and processing steps required to manufacture integrated circuits, the higher the associated costs to manufacture the integrated circuits. Further, simply employing the lower voltage devices for higher voltage I/O applications is also not desirable since such lower voltage devices may be overstressed and their reliability would be decreased, or altogether damaged and performance and functionality would be compromised.